1. Field of the Invention
The present invention relates to a thin film deposition method and a thin film deposition apparatus. More particularly, it relates to a thin film deposition method adapted to check and determine the number of particles generated in an etching process for the purpose of wafer surface cleaning, which is performed in advance of a thin film deposition process, and to remove undesirably deposited films from which the particles may generate, the method thereby enabling appropriate and easy removal of the particles. Furthermore, it relates to a thin film deposition apparatus having an arrangement for the removal of the particles.
2. Description of the Related Art
A sputtering apparatus for mass-production performs the processing of a plurality of wafers by employing a multi-chamber structure which mainly comprises a plurality of processing chambers. The sputtering apparatus having the multi-chamber structure has arrangements for preventing air in the atmosphere from entering the inside of the apparatus, and for preventing target materials in the individual processing chambers from being contaminated with substances introduced from other chambers. With such arrangements, therefore, the apparatus is able to perform sputtering which allows thin films having stable quality levels to be formed. Conventionally, in general, with a view to removing oxide films or contamination naturally generated on the surfaces of wafers, an etching process has been performed before the sputtering process, in which the wafer surfaces are subjected to etching. In the etching process, discharge is caused in, primarily, an argon (Ar) gas, so as to etch the wafer surfaces (as disclosed in, for instance, Japanese Patent Laid-Open No. 2-183531). In general, the etching process is referred to as "a pretreatment process" for fabricating a semiconductor circuit. The etching process is generally performed in a vacuum chamber which is, in the sputtering apparatus, used exclusively for this purpose.
A conventional thin film deposition method including the etching process as the pretreatment process in advance of the sputtering process, has the following problem in relation to particles.
A phenomenon caused by the etching of the conventional method will be described with reference to FIGS. 7 and 8. Referring to FIG. 7, in a vacuum chamber 71 in which etching is to be performed, a wafer 73 (for example, a silicon substrate) held by a wafer holder 72 is disposed at an upper position. A counter electrode 75 housing a magnet 74 for magnetron discharge is disposed at a lower position in the vacuum chamber 71. The vacuum chamber 71 is equipped with a main pump 76, and an Ar gas introducing system 77. The main pump 76 is comprised of a high vacuum pump such as a cryopump or a turbo-molecular pump. A high-frequency power source 79 is connected between the wafer holder 72 and the counter electrode 75. After a predetermined pressure has been attained and set in the chamber 71 by the main pump 76, Ar gas is introduced into the chamber 71 by the Ar gas introducing system 77. Thereafter, when a high-frequency power is applied by the high-frequency power source 79, magnetron discharge is caused by crossed electric and magnetic fields. When the magnetron discharge occurs, its self-bias effect causes argon ions 80 to be impinged onto the surface (facing the counter electrode 75) of the wafer 73, thereby etching the surface of the wafer 73.
FIG. 8 shows a state in the above-described etching (i.e., etching process as the pretreatment process). Referring to FIG. 8, when the surface of the wafer 73 is etched with the argon ions 80, silicon atoms 81 are ejected by the etching, and deposit on the counter electrode 75 and the inner wall of the vacuum chamber 71, etc., thereby forming silicon films. When the silicon films have grown to have a certain film thickness, they exfoliate due to internal stress, thereby causing the generation of a great number of particles in the vacuum chamber 71. When a great number of particles are thus generated, some of them may adhere to the surface of the wafer 73, thereby entailing the risk of a serious adverse influence on fine wiring structures. In consequence, the above-described phenomenon results in the problem of a reduction in the yield of products.
A conventional method directed to preventing the generation of particles is basically a method which copes with the silicon films formed on the inner wall of the vacuum chamber 71 by arranging shield plates 82 in the vicinity of the inner wall surfaces, and replacing the shield plates 82 when the silicon films have grown to have a predetermined thickness. The conventional method copes with the film formation on the counter electrode 75 by directly replacing the counter electrode itself when the thickness of the silicon films has become a predetermined value. However, these operations of the conventional method are performed by interrupting the successive process, and rendering the inside of the vacuum chamber exposed to air. The conventional method is disadvantageous in that the production efficiency of the thin film deposition, and hence, that of the semiconductor device fabrication, drops. For instance, when fifty wafers are etched and, thereafter, the shield plates as well as the counter electrode are replaced, the entire process requires a period of about six hours.
Other methods have been proposed to remove undesirably deposited films from the inner wall of the vacuum chamber (or vessel) and the counter electrode, as well as the particles generated from the films or the same. In these methods, a gas for cleaning is introduced into the vacuum vessel, and dry etching, or plasma etching, is performed in order to remove the undesired deposited films on the inner wall of the vacuum vessel, etc. (Japanese Patent Laid-Open Nos. 2-94522, 1-315137, 2-214118, and 2-250325). With these methods for the removal of the deposited films on the vacuum vessel inner wall, etc. disclosed in the above-identified documents, it is possible to perform a removing operation while the inside of the vacuum vessel is maintained in a vacuum condition. Accordingly, it is possible to improve the speed of the removing operation while keeping the vacuum chamber vacuum. However, the documents do not specifically describe the conditions under which and the timing at which the removing operation should be performed, thus making it necessary for the methods to be further improved when they are to be actually put into practice.
Other related arts are respectively described in, for example, Japanese Patent Laid-Open Nos. 2-39530, 2-89313, and Japanese Patent Post Exam Publin No. 63-39676.
The above-described problem that the sputtering apparatus for mass-production meets, may also arise in other similar thin film deposition apparatuses.